This invention relates generally to the field of telecommunications and in particular to a network interface card (NIC) for wireless communications and networking over an Asynchronous Transfer Mode (ATM) network and which provides high throughput for hosts of the network.
Asynchronous Transfer Mode (ATM) has long been advocated as an important technology for interconnecting wide area heterogeneous networks. In networks constructed utilizing ATM technologies, transported data is divided into small, fixed length units called cells. These cells are further divided into a header and data portion, with the header portion comprising identification, priority and routing information, and the data portion comprising actual data transported between systems.
An important distinguishing characteristic of ATM and networks constructed therefrom, is that it is an end-to-end technology, meaning that with ATM networks the protocols (ATM) are uniform throughout the entire network. That is to say, the ATM on the desktop is the same as the ATM on the Local Area Network (LAN), is the same as the ATM on the Wide Area Network. Consequently, organizations that employ ATM networks do not need extra equipment (like routers or gateways) to interconnect their networks thereby reducing the cost and complexity of the networks while at the same time improving their flexibility.
Due to these and other inherent advantages, there has been widespread and rapid deployment of ATM networks. This rapid deployment of ATM networks, and the contemporaneous need to provide reliable wireless ubiquitous information access to end users, has accelerated the development of Wireless ATM (WATM) networks. Presently, the development of WATM networks is still research oriented, and efforts to specify a standard for its protocol reference architecture are underway. See, for example, the article by D. Raychaudhuri et al., entitled "ATM-Based Transport Architecture for Multiservices Wireless Personal Communication Networks", which appeared in Vol. 12, No. 8 of IEEE JSAC in October 1994, or proceedings. An example of a Wireless ATM network which has been prototyped to ascertain the requirements for future WATM network has been described by D. Raychaudhuri et al., in an article entitled "WATMnet: A Prototype Wireless ATM System for Multimedia Personal Communication", ICC '96.
In WATMnet, as well as in other WATM networks, a Network Interface Card (NIC) is used to interface a piece of equipment to the WATM network. As can be readily appreciated by those skilled in the art, the architecture of a NIC plays an important role when accessing a high-performance network such as ATM. Specifically, the NIC can become a network bottleneck if its throughput characteristics are not taken into consideration while designing its architecture. Since the Data Link Control Layer (DLC), the Media Access Control Layer (MAC), and Physical Radio (RPhy) layers are integrated in a WATM NIC, the WATM NIC's processing requirements are more demanding than that of ATM NICs at equivalent transmission rates. (See, for example, R. Dighe et al., "The Multimedia C&C Platform (MCCP), A Network-Centric Architecture for Multimedia", IEEE ATM Workshop '95, October 1995; and C. A. Johnston, "Architecture and Performance of HIPPI-ATM-SONET Terminal Adapters", IEEE Communications, Vol. 33, No. 4, April 1995.) Thus, the design of a high-throughput WATM NIC software/hardware architecture remains a challenging problem.
Critical for the usefulness of such NIC adapters, is an efficient architecture that can allow network communications to proceed in parallel with other operations on a host without excessively slowing down those operations. Also critical to the efficiency of the entire network is a need that the adapter have minimal latency in reception and transmission of data. At the same time, the adapter must be economical to be suitable for accompanying host equipment.
Therefore, a need exists in the art for apparatus and methods which provide for the efficient and flexible wireless interfacing of computer and other electronic devices to ATM networks.